Study of the Relation Between Molecular Structure and Mesomorphic Behavior with Reference to a Novel Homologous Series: α-3-[4′-n-Alkoxy benzoyloxy] phenyl-β-3^″-Nitro benzoyl ethylenes

Abstract

The synthesis and mesomorphic properties of a novel homologous series is reported. With the exception of the methyl and ethyl homologues, all 11 members of the series exhibit mesomorphism enantiotropically. The propyl to pentyl homologues, and the tetradecyl and hexadecyl homologues are enantiotropic nematic without the exhibition of smectic mesomorphism; while the hexyl to dodecyl homologues exhibit smectic mesomorphism in addition to the nematic phase. The texture of the nematic-mesophase by optical polarizing microscopy is of the threaded or Schlieren type, and that of smectogenic homologues is of the focalconic fan type. A phase diagram of the series shows a typical trend. Analytical and spectral data confirm the molecular structure of the compounds. Transition temperatures and mesomorphic properties are determined by optical polarizing microscopy. Smectic and nematic thermal stabilities are 125°C and 167°C, respectively. The series is predominantly nematogenic and partly smectogenic with middle-order melting type, and the smectic and nematic-mesophase ranges vary from 8°C to 22°C and 9°C to 56°C, respectively. The mesomorphic properties of the novel series are compared with other structurally similar homologous series.

Keywords:

• Enantiotropy
• liquid crystals
• mesomorphism
• nematic
• smectic

Acknowledgments

Authors thank to authorities of K.K. Shah Jarodwala Maninagar Science College and S.P.T. Arts & Science College, Godhara for their valuable cooperation in present work. Authors are also thankful to Vaibhav laboratory for their analytical services. Thanks are due to the Ankita Doshi, Department of Biochemistry, M.S. University of Baroda, Vadodara for valuable support in the work.